Gooch and Ensign — Determination of Bromine. 147 



VIII. 



H. 2 S0 4 HN0 3 Fe 2 (S0 4 )s HBr = KBr 



[1:1] 







taken. 





volume. 



volume. 



in ike distill 



ate. lost. 



em 3 . 



cm 3 . 



grm. 



* grm. 



grm. 



cm 3 . 



cm 3 . 



grm. 



grm. 





5 



9 



0-6799 



1 



600 



500 



00021 



0-0008 





5 



2 



0-6799 



1 



500 



400 



0-0036 



0-0016 



10 



5 



2 



0-6799 



1 



600 



500 



0-0037 



0-0016 



10 



5 



2 



0-6799 



1 



500 



4C0 



0-0082 



0-0035 



From the experiments of series I, it becomes plain that 5 

 cm 3 of strong sulphuric acid (added as 10 cm 3 of the mix- 

 ture made by diluting the strong acid with an equal volume of 

 water) and 1 grm. of potassium bromide do not interact in a 

 way to set bromine free or to volatilize hydrobromic acid ap- 

 preciably until the volume of the liquid has decreased by boil- 

 ing to about 100 cm 3 . The results of series II show, in like 

 manner, 'that the effect of 3 cm 3 of nitric acid — the amount 

 which was found to be suitable in the separation of iodine and 

 chlorine in presence of a ferric salt — is not significant until 

 the liquid is concentrated to 200 cm 3 . The combined eifect of 

 the two acids, as shown in the experiment of Series III, is 

 somewhat different. Here it is evident that bromine is liber- 

 ated at the highest degree of dilution employed, though the 

 loss is hardly significant in a volume of liquid larger than 

 400 cm 3 . In the experiments of series TV, the effect of in- 

 creasing the proportions of nitric acid, while keeping the 

 amount of sulphuric acid and the degree of change in dilution 

 constant, was manifestly to magnify the decomposition of the 

 hydrobromic acid. 



In series V to VIII, hydrobromic acid was employed instead 

 of the bromide. From the results of series V, it becomes evi- 

 dent that concentration of the pure hydrobromic acid may be 

 pressed to 15 cm 3 without incurring serious loss. The effect of 

 the presence of sulphuric acid in raising the limit below which 

 the volatilization of hydrobromic acid begins appreciably, is 

 plain in the figures of series VI. Series YII sets the volume of 

 400 cm 3 as the limit to which the same amount of hydrobromic 

 acid may be concentrated without loss in presence of 5 cm 3 of 

 nitric acid. Series Till indicates unmistakably that even at a 

 volume of 500 cm 3 the combined influences of sulphuric acid, 

 nitric acid and ferric sulphate taken in the amounts named 

 remove bromine, the loss being greater when the sulphuric 

 acid is present than is the case when the nitric acid and ferric 

 sulphate are present without it. 



The general indication of all these results taken together 

 and brought into comparison would seem to be that improve- 

 ment in the processes for separating iodine by the use of the rea- 

 gents whose action is here studied should lie in the direction of 

 greater dilution of the solution treated. Accordingl} 7 certain 



